Pressure wave supercharger

ABSTRACT

A pressure wave supercharger includes a cell rotor which is arranged in the housing and driven by an electric motor. The electric motor includes a rotating member which is connected to the cell rotor, and a fixed member. A bearing assembly is provided to simultaneously support the cell rotor within the housing and the rotating member in relation to the fixed member.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application claims the priority of German Patent Application, Serial No. 10 2010 011 147.3-15, filed Mar. 11, 2010, pursuant to 35 U.S.C. 119(a)-(d), the content of which is incorporated herein by reference in its entirety as if fully set forth herein.

BACKGROUND OF THE INVENTION

The present invention relates to a pressure wave supercharger for installation on an internal combustion engine of a motor vehicle.

The following discussion of related art is provided to assist the reader in understanding the advantages of the invention, and is not to be construed as an admission that this related art is prior art to this invention.

Internal combustion engines for motor vehicles are supercharged to increase efficiency. The gas exchange is improved during the intake cycle through increase of the charging degree of the cylinder. Supercharged engines consume less fuel compared to engines that are not charged. A supercharged motor is able to burn a same amount of air-fuel mixture as an engine with greater capacity, when the internal resistance is the same.

Supercharging systems to generate gas dynamic processes in closed gas channels for supercharging internal combustion engines are generally designated as pressure wave superchargers or pressure wave machines. Cell rotors used in pressure wave machines have typically a cylindrical configuration and have channels which have predominantly constant cross section and extend from the hot gas side to the cold gas side.

Pressure wave superchargers are currently operated by electric motors to replace belt drives used before to drive a cell rotor. Electric motors are connected via a coupling directly with the rotor shaft. As a result, the rotation speed can be freely selected within functional requirements depending on the operating state and independently controlled by the rotation speed of the crankshaft of the internal combustion engine.

As the available installation space in proximity of the internal combustion engine is limited, pressure wave superchargers should be dimensioned as compact as possible. In addition, the electric power consumption should be minimized. Thus, force-locking connections such as couplings and bearings should be dimensioned to encounter smallest possible friction while still realizing maximum system stiffness. To provide the required system stiffness to oppose flexure and vibration behavior, the provision of a combination of fixed bearing and movable bearing is proposed for the cell rotor or cell rotor shaft in order to secure these components in an axial position. The electric motor coupled to the shaft has hereby a separate bearing. The individual lengths and the individual frictions encountered in the bearings add to a total length and total friction, respectively, which adversely affect power loss of the rotor drive and structural size.

It would therefore be desirable and advantageous to address these problems and to obviate other prior art shortcomings.

SUMMARY OF THE INVENTION

According to one aspect of the present invention, a pressure wave supercharger includes a housing, a cell rotor arranged in the housing, an electric motor for driving the cell rotor, the electric motor including a rotating member which is connected to the cell rotor, and a fixed member, and a bearing assembly to simultaneously support the cell rotor within the housing and rotatably support the rotating member in relation to the fixed member.

The present invention resolves prior art problems by providing an electric motor which is configured as electromotive converter with a rotating member and a fixed member to generate mechanical energy. Friction is kept to a minimum by supporting the cell rotor in relation to the housing by the same bearing assembly that is provided to also support the fixed member (armature) in relation to the rotating member (stator) of the electric motor.

By providing a common bearing assembly, individual lengths of the components, i.e. bearings, can be reduced. The number of bearing points is reduced so that less friction is encountered and thus also less power loss. At the same time, the decrease in bearing components results in a pressure wave supercharger which can be made compact, lightweight, and thus requires less installation space.

According to an advantageous embodiment of the present invention, a cell rotor shaft can extend in one piece through the electric motor and is connected to the cell rotor, wherein the rotating member is mounted to the cell rotor shaft and surrounded by the fixed member to configure the electric motor as an internal rotor, with the bearing assembly supporting the cell rotor shaft and thereby supporting the rotating member in relation to the fixed member and supporting the cell rotor in relation to the housing. The fixed member is hereby secured to the housing. As the single-piece cell rotor shaft extends from the cell rotor and through the electric motor, the need for a separate output shaft of the electric motor and a coupling to connect a cell rotor shaft with the output shaft is now eliminated. The single-piece cell rotor shaft upon which the rotating member (armature) is arranged thus extends from the cell rotor. A first bearing point of the bearing assembly may hereby be provided between the cell rotor and the electric motor.

According to another advantageous feature of the present invention, the cell rotor shaft can be configured to taper in steps from the cell rotor in a direction of the electric motor. This creates bearing seats such as snug fits for bearings and also the required seat for the armature. A benefit of a configuration involving a shaft which extends from the cell rotor is the possibility to secure all following components in succession through shrinkage or pressing. When configured as an internal rotor, the electric motor is supported on the shaft of the cell rotor but not vice versa. The supporting cell rotor shaft may thus also be designated as a cell rotor shaft having bearing points on one side of the cell rotor but on both sides of the electric motor.

By eliminating the need for a bearing that is specifically provided for the electric motor, it is possible to install the electric motor virtually in a riding manner on the cell rotor shaft. The electric motor in turn is integrated in the housing of the pressure wave supercharger. There is no need for a separate housing for the electric motor. This saves weight and space. An essential feature, however, is the presence of a bearing assembly which supports the cell rotor shaft and at the same time supports the electric motor.

According to another advantageous embodiment of the present invention, the bearing assembly may include a bearing pin which is connected to the housing, with the fixed member being mounted to the bearing pin and surrounded by the rotating member to configure the electric motor as an external rotor, with the rotating member being connected to the cell rotor. The outer member of the electric motor is thus configured as rotating outer member which is connected with the cell rotor. The fixed member of the electric motor is thus positioned on the inside and arranged on the bearing pin. Suitably, the bearing pin is configured as hollow pin.

According to another advantageous feature of the present invention, the electric motor may be accommodated in the cell rotor. As a result, the electric motor is not positioned in axial offset relation to the cell rotor but is located directly inside the cell rotor. While this configuration may result in a cell rotor of greater diameter, its length is significantly reduced compared to a solution with axially offset electric motor.

The compact size with fixed hollow bearing pin allows the energy supply to the electric motor to be provided through the bearing pin. In addition, it is also possible to incorporate a coolant supply and coolant removal through the bearing pin. An example of coolant is fresh air that is drawn into the pressure wave supercharger. The coolant supply thus involves a vent channel.

In both the internal rotor variation and external rotor variation, a pivot bearing pair can be provided to support the armature together with the cell rotor in relation to the stator or housing. The housing provides hereby a torque support for the cell rotor and the armature. The cell rotor is thus rotatably supported solely by the pivot bearing pair in relation to the housing.

According to another advantageous feature of the present invention, an axial compressor can be arranged on the cell rotor shaft and constructed to raise a pressure level of cooling air being drawn into the cell rotor. Suitably, the axial compressor is positioned upstream (anteriorly) of the electric motor. The axial compressor forces a coolant flow through one or more compressor stages (bladed wheels).

Cooling of the stator winding of the electric motor is realized via the laminated stator core and the intake of fresh air which flows through the fan of the pressure wave supercharger. Heat dissipation takes place by heat conduction and convection and/or separate cooling channels which divert a portion of intake air directly to motor cooling.

A pressure wave supercharger according to the present invention has many benefits, which include compact size as a result of a reduced total system length. Compared to prior art approaches, at least three components are eliminated, namely a motor bearing, a coupling, and a motor support or motor flange. There is no friction between motor bearing and possible coupling frictional forces. The mass moment of inertia is reduced and smaller acceleration forces are required so that the pressure wave supercharger according to the invention can respond much faster.

BRIEF DESCRIPTION OF THE DRAWING

Other features and advantages of the present invention will be more readily apparent upon reading the following description of currently preferred exemplified embodiments of the invention with reference to the accompanying drawing, in which:

FIG. 1 is a schematic illustration of one embodiment of a drive unit for operating a pressure wave supercharger;

FIG. 2 is a schematic illustration of another embodiment of a drive unit for operating a pressure wave supercharger;

FIG. 3 is a schematic illustration of the drive unit of FIG. 1 with incorporation of an axial compressor;

FIG. 4 is a partly sectional schematic illustration of the drive unit of FIG. 2;

FIG. 5 is a sectional view, on an enlarged scale, of a detail of yet another embodiment of a drive unit for operating a pressure wave supercharger; and

FIG. 6 is a sectional view of still another embodiment of a drive unit for operating a pressure wave supercharger.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Throughout all the figures, same or corresponding elements may generally be indicated by same reference numerals. These depicted embodiments are to be understood as illustrative of the invention and not as limiting in any way. It should also be understood that the figures are not necessarily to scale and that the embodiments are sometimes illustrated by graphic symbols, phantom lines, diagrammatic representations and fragmentary views. In certain instances, details which are not necessary for an understanding of the present invention or which render other details difficult to perceive may have been omitted.

Turning now to the drawing, and in particular to FIG. 1, there is shown a schematic illustration of one embodiment of a drive unit for operating a pressure wave supercharger of which only a cell rotor 2 is illustrated for the sake of simplicity. The cell rotor 2 is rotatably supported in a housing which is not shown here in greater detail. The drive unit includes an electric motor 1 which drives the cell rotor 2 via a cell rotor shaft 3 which is supported by bearings 4 and 5 on both sides of the electric motor 1, with the bearing 4 positioned between the cell rotor 2 and the electric motor 1. The cell rotor shaft 3 is formed of one piece and guided through the electric motor 1.

The electric motor includes a rotating member 6 (rotor or armature) which is arranged on the cell rotor shaft 3 and a fixed member 7 (stator) which is disposed in surrounding relation to the rotating member 6. As in the embodiment of FIG. 1, the rotating member 6 is positioned on the inside, this type of electric motor 1 is called an internal rotor. The bearings 4, 5 thus provide support of the cell rotor 2 in relation to the housing as well as support of the inner rotating member 6 in relation to the outer fixed member 7.

As shown by way of example in FIG. 3, the pressure wave supercharger has an axial compressor 19 which is arranged on the cell rotor shaft 3 and constructed to raise a pressure level of cooling air being drawn into the cell rotor 2. The axial compressor 19 is hereby positioned upstream of the electric motor 1.

FIG. 2 shows an alternative embodiment of a drive unit for operating a pressure wave supercharger of which again only the cell rotor 2 is illustrated for the sake of simplicity. The drive unit includes an electric motor 8 which is arranged within the cell rotor 2 and configured in the form of an external rotor with an outer rotating member 9 and an inner fixed member 11. The rotating member 9 rotates hereby together with a hub 10 of the cell rotor 2 about the fixed member 11 which is secured to a bearing pin 12 that is connected to housing 16 and configured as a hollow pin having channels 20 formed therein for circulation of a coolant, as shown in particular in FIG. 4. Bearing 13 is arranged on one side (here on the left-hand side of the drawing plane) of the electric motor 8 between the hub 10 of the cell rotor 2 and the bearing pin 12 and is configured as tapered roller bearing and thus constitutes a fixed bearing. Bearing 14 is arranged on the other side (here on the right-hand side of the drawing plane) of the electric motor 8 between a support 17 and a journal 18 of the bearing pin 12 and is configured as a movable bearing/guide bearing. A screen 15 protects the bearing 14 from the hot-gas side.

The electric motor 8 is cooled by cooling air sucked in and forced to flow through passageways (not shown) in the bearing pin 12. As indicated by arrows P in FIGS. 2 and 4, the cooling air exits the bearing pin 12 in proximity of the bearing 14 and is deflected radially for flow to the electric motor 8.

Although not shown in detail, the bearing pin 12 may accommodate also an energy supply for the electric motor 8.

Referring now to FIG. 5, there is shown a sectional view, on an enlarged scale, of a detail of yet another embodiment of a drive unit for operating a pressure wave supercharger. In this embodiment, provision is made for an electric motor 1 which is accommodated in the cell rotor 2. As a result, the electric motor 1 is not positioned in axial offset relation to the cell rotor 2 but is located directly inside the cell rotor 2.

FIG. 6 is a sectional view of still another embodiment of a drive unit for operating a pressure wave supercharger. Parts corresponding with those in FIG. 1 are denoted by identical reference numerals and not explained again. The description below will center on the differences between the embodiments. In this embodiment, the outer part of the electric motor 1 is configured as rotating outer rotating member 6 which is connected to the cell rotor 2 via the cell rotor shaft 3 which is configured as a hollow shaft. The fixed member 7 of the electric motor 1 is positioned inwards and arranged on bearing pin 12 which is connected to the housing 16. The electric motor 1 is thus arranged between the bearing pin 12 and the hollow cell rotor shaft 3.

While the invention has been illustrated and described in connection with currently preferred embodiments shown and described in detail, it is not intended to be limited to the details shown since various modifications and structural changes may be made without departing in any way from the spirit and scope of the present invention. The embodiments were chosen and described in order to explain the principles of the invention and practical application to thereby enable a person skilled in the art to best utilize the invention and various embodiments with various modifications as are suited to the particular use contemplated.

What is claimed as new and desired to be protected by Letters Patent is set forth in the appended claims and includes equivalents of the elements recited therein: 

What is claimed is:
 1. A pressure wave supercharger, comprising: a housing; a cell rotor arranged in the housing; an electric motor for driving the cell rotor, said electric motor including a rotating member which is connected to the cell rotor, and a fixed member; and a bearing assembly to simultaneously support the cell rotor within the housing and rotatably support the rotating member in relation to the fixed member.
 2. The pressure wave supercharger of claim 1, further comprising a cell rotor shaft upon which the cell rotor is mounted and which extends in one piece through the electric motor, wherein the rotating member is mounted to the cell rotor shaft at a distance to the cell rotor and surrounded by the fixed member to configure the electric motor as an internal rotor, said bearing assembly having a first bearing supporting the cell rotor shaft in a space between the electric motor and the cell rotor and a second bearing supporting the cell rotor shaft at an opposite side of the electric motor distal to the first bearing.
 3. The pressure wave supercharger of claim 1, wherein the bearing assembly includes a bearing pin which is connected to the housing and extends in one piece through the electric motor, said fixed member being mounted to the bearing pin and surrounded by the rotating member to configure the electric motor as an external rotor.
 4. The pressure wave supercharger of claim 3, wherein the bearing assembly has a first bearing to support the bearing pin on one side of the electric motor and a second bearing to support the bearing pin on another opposite side of the electric motor.
 5. The pressure wave supercharger of claim 3, wherein the electric motor is accommodated in the cell rotor.
 6. The pressure wave supercharger of claim 3, wherein the bearing pin is configured as hollow shaft having channels formed therein for circulation of a coolant.
 7. The pressure wave supercharger of claim 2, further comprising an axial compressor arranged on the cell rotor shaft and constructed to raise a pressure level of cooling air being drawn into the cell rotor.
 8. The pressure wave supercharger of claim 7, wherein the axial compressor is positioned upstream of the electric motor.
 9. The pressure wave supercharger of claim 2, wherein the cell rotor shaft is configured to taper in steps from the cell rotor in a direction of the electric motor.
 10. A pressure wave supercharger, comprising: a cell rotor shaft; a cell rotor arranged in a housing and mounted on the cell rotor shaft; an electric motor driving the cell rotor and configured as an internal rotor to include an inner rotating member which is connected to the cell rotor, and an outer fixed member, said cell rotor shaft being configured to extend in one piece through the electric motor; and a bearing assembly supporting the cell rotor shaft and simultaneously supporting the rotating member in relation to the fixed member and supporting the cell rotor in relation to the housing.
 11. The pressure wave supercharger of claim 10, further comprising an axial compressor arranged on the cell rotor shaft and constructed to raise a pressure level of cooling air being drawn into the cell rotor.
 12. The pressure wave supercharger of claim 11, wherein the axial compressor is positioned upstream of the electric motor.
 13. A pressure wave supercharger, comprising: a housing; a cell rotor arranged in the housing; and an electric motor for driving the cell rotor, said electric motor being configured as an external rotor to include an outer rotating member which is connected to the cell rotor, and an inner fixed member, said electric motor having a bearing pin connected to the housing upon which the fixed member is arranged.
 14. The pressure wave supercharger of claim 13, wherein the electric motor is accommodated in the cell rotor.
 15. The pressure wave supercharger of claim 13, wherein the bearing pin is configured as hollow pin and constructed to include a coolant supply. 